Piseco Lake Association – 2017 Annual Meeting

Engineering Services – Pisecto Lake Outlet Dam

Kevin Ruswick, PE, CFM

August 19, 2017 Presentation Outline

Introductions / Firm Qualifications

Dam Information

Review the Town’s Concerns

Preliminary Study

Refined Analysis

Study Status

Q&A INTRODUCTIONS / QUALIFICATIONS

Piseco Lake Outlet Dam viewed from the Route 10 Bridge. Schnabel and Dam Engineering

Schnabel has over 300 employees, of which more than 100 are dedicated to dam safety projects and work exclusively in this field. These include all disciplines to support dam safety projects.

In the last 20 years our firm has completed more than 2,000 dam and water resource projects.

We believe that hiring a firm that specializes in dam engineering will result in a superior project outcome. Schnabel and Dam Engineering Schnabel and Dam Engineering

Regional Schnabel Dam Projects Project Team

Project Manager & H&H Lead Kevin Ruswick, PE, CFM KEVIN RUSWICK H&H, Dam Engineering Senior Reviewer Gregory Daviero, PhD, PE Michael Taylor, PE

MICHAEL TAYLOR Geotechnical / Hydrology & Hydraulics Geotechnical Dam Engineering Kevin Ruswick, PE, CFM Brian Toombs, PE David Railsback, PE Keith Toombs, EIT DAVID RAILSBACK H&H, Dam Engineering All members of the Project Team are located in our Clifton Park, NY office. Recent New York State Dams Experience

Schnabel has worked on over 40 dams in New York State, including:

NYS DEC – Hazard Screenings & Hazard Classifications for 23 DEC-Owned Dams including Lake Durant Dam, Lake Clear Outlet Dam, Kunjumuk Creek Dam, Hillabrandt Vly Dam

Hudson River Black River Regulating District – Conklingville Dam (Great Sacandaga Lake)

City of Plattsburgh – Mead Reservoir Dam, Westbrook Reservoirs No. 1 & 2

Town of Wilmington – Wilmington Dam

City of Saratoga Springs – Loughberry Lake Dam

NYC DEP– Cannonsville Reservoir Dam

Albany Water Board – Alcove Reservoir Dam, Basic Reservoir Dam, Loudonville Reservoir Dam, Rensselaer Lake Dam Kunjumuk Creek Dam (NYS DEC) DAM INFORMATION

Piseco Lake Outlet Dam viewed from Left Abutment. Dam Details (NYSDEC)

West Branch of Sacandaga River (59.4 sq. mi.) Original Construction in 1888 (Timber Crib) Dam Modified in 1950’s – 1960’s Concrete and Earthen Embankment 65-ft long, 6-ft max height Storage – 164,386 ac-ft Mostly inactive storage NYS DEC Class A Structure Stop Logs to Manage Lake Levels (May - Oct) Watershed Information 59.2 sq. mi. at Route 8 Bridge 63.9 sq. mi. at Dam 80% Forest Land 19% Lakes/Wetlands Piseco Lake – 4 sq. mi. 1% Developed/Urban Land REVIEW OF THE TOWN’S CONCERNS

Piseco Lake Outlet Dam viewed from Right Abutment. 2015 MBP Condition Inspection

Short-Term Recommendations: Remove Trees and Brush Repair Undermined Concrete at Left Abutment Wall Remove Apron Timbers and Install Engineered Riprap Blanket at Toe Armor Left Embankment Abutment Repair Leakage Through Left Abutment Alternate Flashboard (3-ft, 4-ft) Placement Replace Flashboards and Install Walkway Install Warning Signs and Fence 2015 MBP Condition Inspection

Long-Term Recommendations: Topographic and Bathymetric Survey Hydrologic and Hydraulic Analysis Collect Soil Borings Structural Stability Analysis Develop Conceptual Design and Cost Estimate  Address Dam Safety Deficiencies  Consider Automated Flashboards and/or Spillway Gates  Spillway Apron Repair  Increase Spillway Capacity, Raise/Protect Abutments Final Design & Construction Town/PLA Concerns / Desired Improvements

Condition of Dam  Seepage at Left Abutment

 Concrete Deterioration Improve Lake Level Management

 Stoplogs vs. automated/gates or rubber dam

Regulatory Compliance Environmental Stewardship and NYSDEC Requirements PRELIMINARY STUDY

Piseco Lake viewed from Route 8 Bridge. Dam Operations and Lake Level Control

Piseco Lake

Route 8 Bridge

Big Bay Route 10 Bridge Dam Narrows (2.7 Miles) (Boulder Channel) Anecdotal Lake Level Data

Water Level at Piseco Lake 506.1 meters (1660.4 ft)

Water Level at Rt 10 Bridge 504.3 meters (1654.5 ft) Preliminary Hydraulic Model Development

USGS 10-meter DEM NYSDOT Data for Route 8 and Route 10 Bridges Preliminary Hydraulic Model Results

0.1 ft +/- (?) Water Surface With All Stoplogs Piseco Lake 3 ft +/- Stoplogs Direction of Flow

2.7 Miles Dam / Route 10 Big Bay Narrows (Boulder Channel) Route 8 Need for Survey to Refine the Hydraulic Model

Narrows Dam (Boulder Channel) ESTABLISH THE ROADMAP

Big Bay viewed from Route 10 Bridge. Suggested Road Map

Data Collection / File Review / Site Visit Survey – Topographic & Bathymetric  Establish Datum for current lake level gage & add staff gage at the dam. H&H Study – Inflow and Outflow from the Lake/Dam Geotechnical Investigation  Excavations and Maintenance – Test Pits and Backfill with Select Material  Laboratory Testing of Embankment/Foundation Materials Establish Goals and Priorities for Short-Term and Long-Term Repairs and Improvements Develop Scope and Budget to Achieve Objectives Design and Implement Repairs Survey Status

Scope of Work 9 Stream Cross Sections 2 Bridges Piseco Outlet Dam & Site Establish Staff gages at dam & lake Solicited Bids from 6 Local Surveyors 3 Bids Received – Shumaker Engineering - $19,350 Susan Anacker - $11,160 Blanchard Land Surveying - $5,500 Survey Status

Scope of Work 9 Stream Cross Sections 2 Bridges Piseco Outlet Dam & Site Establish Staff gages at dam & lake Solicited Bids from 6 Local Surveyors 3 Bids Received – Shumaker Engineering - $19,350 Susan Anacker - $11,160 Blanchard Land Surveying - $5,500 H&H Study Status

HEC-HMS Hydrologic model developed Waiting for Survey Data to Finalize outflow rating curve & storage rating curve Hydraulic Model – Waiting for Survey Data 2017 Lake Level Monitoring - Ongoing

Lake Level vs. Rainfall 30 6 2.5 inches rain over 5 days raises lake level 2.5 inches rain over 1 day significantly 5 inches. No board raises lake leve. Note change in slope changes 20 when all 4' boards removed. May be 5 from boards or storm shape Boards out long term. Removal response Boards OUT 10 4 complicated by rain Boards IN event 4' Boards HALF Boards IN 4' Boards HALF 0 3 4' Boards OUT Boards IN Lake Level Lake Level (inches)

Lots of rain = increase DailyRainfall (inches) 4' Boards HALF in lake level. Unable to -10 determine affect of 2 4' Boards OUT removing boards All Boards OUT Rainfall

-20 1

-30 0 3/6/2017 0:00 3/26/2017 0:00 4/15/2017 0:00 5/5/2017 0:00 5/25/2017 0:00 6/14/2017 0:00 7/4/2017 0:00 7/24/2017 0:00 8/13/2017 0:00 9/2/2017 0:00 Date Recent Lake Level Monitoring

Lake Level & Big Bay Level Correlate water levels with stop-log operation Big Bay Vs Lake Level Big Bay datum = Dam Crest Lake Level Datum = Unknown 50

40 As boards come out Big bay drops by 3 ft Lake drops by 3 in 30

20

10 Level Level relative toDatum (inches)

0

-10

Date+Time

Boards IN Big Bay Level 4' Boards HALF 4' Boards OUT All Boards OUT Geotechnical Investigation

Explore Left Abutment Seepage Assessment and Material Loss Town is working on arrangements for excavator Evaluate “unseen” below-grade conditions Schnabel is coordinating with local stone suppliers for material availability and specs Schnabel will coordinate with NYSDEC – Dam Safety to assess maintenance permitting requirements Questions SUPPLEMENTAL INFORMATION

Piseco Lake viewed from Route 8 Bridge. Bathymetric Map Piseco Saw Mill USGS Topographic Map - 1906 USGS Topographic Map - 1954 SIMILAR PROJECTS

Route 10 Bridge. Case Study: Otsego Lake Dam – Cooperstown, NY

Dam is located approximately 1-mile from Otsego Lake. Schnabel performed Hydrology & Hydraulics analyses to evaluate flood reduction alternatives. Channel and constrictions between lake and dam limited outflows from lake. Schnabel performed hazard class assessment and lowered from Class B to Class A. Case Study: Wilmington Dam Operational Improvements

At Wilmington Dam, the existing outlet gate does not allow much flexibility with respect to installing and removing stop logs. We are helping the Town improve operations by designing and installing a new low-level gate. We made use of hydrologic and hydraulic models to design a practical and cost-effective solution, which is pending construction. Case Study: Mead Reservoir Dam – Plattsburgh, NY

At Mead Reservoir Dam we utilized refined hydrologic modeling to reduce (by a factor of two) the spillway design flood which had been developed by another consultant.

Schnabel’s approach was approved by NYS DEC and represents an estimated $3M in construction cost savings for the City.

We are currently developing rehabilitation designs for the new spillway. Case Study: Sugar Hollow Dam – Crozet, VA